1. Field of the Invention
This invention relates to a recording paper, in particular, a recording paper useful for color recording carried out by ink-jet recording, and an ink-jet recording process and recording system making use of such a recording paper.
2. Related Background Art
Ink-jet recording has attracted notice because of its readiness for the achievement of high-speed recording, color recording and high-density recording, and recording apparatuses making use of the ink-jet recording have come into wide use. In such ink-jet recording, exclusive coated paper is used, as disclosed, for example, in Japanese Patent Application Laid-open Nos. 59-35977 and 1-135682. The exclusive coated paper comprises base paper whose surface is completely coated with a pigment. The coated paper is suited for forming highly minute and sharp images but has the following problems.
1) It lacks the handling properties of plain paper (e.g., PPC paper and general-purpose woodfree paper). PA1 2) It has a poor writability with pencils. PA1 3) It may cause paper dust due to fall of coat layers. PA1 4) It has no general-purpose properties (i.e., can not be used for other recording processes). PA1 5) It requires a higher production cost than plain paper. PA1 1) It has so poor an ink absorption that the ink may slowly dry and fix when the ink is imparted in a large quantity. If something touches the recording surface in the state the ink is undried and unfixed, images are damaged. PA1 2) Ink runs along fibers of paper when it is absorbed into the paper layer, and hence dots may become too large, or dots may have roughly irregular, or blurred outlines. Hence, no clear letters or characters and images can be obtained. PA1 3) In an attempt to obtain color images, no satisfactory images can be obtained since inks with a plurality of colors are superimposed one after another before they fix to paper and hence the colors are blurred or non-uniformly mixed with one another at the boundaries of images with different colors (hereinafter, this phenomenon is called "bleeding"). PA1 4) Since water-soluble recording agents are used, the recorded images can have no satisfactory water fastness. PA1 5) Coloring materials can exhibit no satisfactory color forming performance. PA1 Ka.sub.1 .ltoreq.5.0 PA1 5.0&lt;Ka.sub.2 .ltoreq.15.0
Herein, the plain paper refers to PPC paper, general-purpose woodfree paper, etc. Examples of plain paper may include toner transfer paper (PPC paper) for electrophotographic recording, nowadays widely used in offices, as disclosed in Japanese Patent Application Laid-open Nos. 51-13244, 59-162561 and 59-191068.
As in the plain paper typified by such transfer paper, conventional recording paper whose pulp fibers are entirely bare to the paper surface has the following problems.